In manufacturing, mining, construction, transportation, and other fields of endeavor, it is often necessary to convert stored energy into mechanical energy. While internal combustion (IC) engines remain a prominent means for meeting this end, electric motors are increasingly preferred for the benefits they provide relative to their IC counterparts. For example, electric motors tend to be much quieter and emit less pollution than equivalent IC engines. Moreover, the conversion of stored electrical energy to mechanical energy may be reversed, and the same basic system used to convert excess mechanical energy into stored electrical energy.
However, powerful electric motors and generators do require cooling in some situations, both to maintain efficiency and to avoid damage. An electric generator (as used herein, the term generator will refer generally to the described physical configuration, whether the device acts as a motor, generator, alternator, rotary converter, etc.) typically includes a stator, which is stationary, i.e., non-rotating, and a rotor, which rotates within the stator, separated by an air gap from the inner surface of the stator assembly. Some devices alternatively employ an “out runner” or “inside out” configuration, wherein the rotor is external to and surrounds the stator.
Regardless of the overall motor configuration, the stator generally comprises a core of ferromagnetic material and windings, consisting of coils of insulated wires or conductors, wound about pole pieces. The rotor may also include a core of ferromagnetic material. The construction of cores, e.g., from laminations or otherwise, and of windings and other physical aspects of traditional motors, while generally relevant, will not be discussed further herein as those of skill in the art will be familiar with traditional motor constructions.
In high-power systems, the substantial current densities and rapidly changing flux densities experienced by the stator can lead to excess heat generation in the stator. This excess heat can lead to inefficient operation, due, for example, to increased electrical impedance in the windings, as well as to damage to the windings or other components. To this end, generators intended for high-output (or high efficiency) may employ a mechanism for cooling the stator and dissipating excess heat. For example, a metal housing having fins may be adhered to or around the stator core, and the excess heat dissipated by a flow of air or fluid over the fins. Fluid cooling systems of certain other configurations have been tried as well.
The inventors have discovered that in practice there is non-uniform cooling when employing any of the prior cooling systems, in that hot spots and cool spots exist during operation. In this situation, even when the temperature at the point of application of the cooling means is well within bounds, the temperatures at other points in the system may be at or beyond a level where damage or substantial loss of efficiency set in. Thus, there is an unfilled need for a fluid cooling system capable of efficiently and uniformly cooling the stator in generator systems.